Field
Exemplary embodiments of the present disclosure relate to a light emitting diode, a method of manufacturing the same, and a light emitting device module including the same, and more particularly, to a light emitting diode having improved reflectance, a method of manufacturing the same, and a light emitting device module including the same.
Discussion of the Background
Gallium nitride (GaN) light emitting diodes (LEDs) have been applied to various fields, such as natural color LED display devices, LED traffic signals, white LEDs, and the like.
A light emitting diode refers to a device that emits light through recombination of electrons and holes in an active layer. The active layer is provided at opposite sides thereof with a p-type semiconductor layer and an n-type semiconductor layer, respectively, such that electrons and holes injected into the active layer are recombined therein to generate light upon application of voltage to an interface between the p-type semiconductor layer and the n-type semiconductor layer.
A flip-chip light emitting diode (LED) has a structure wherein light generated from the active layer is emitted through a transparent substrate, and is generally configured to reflect light towards the transparent substrate using an electrode formed on the p-type semiconductor layer or the n-type semiconductor layer as a reflective electrode. Particularly, various electrode structures have been suggested in order to assist in current spreading in a large flip-chip light emitting diode while improving light output.
However, since there is a limit in improvement of reflectance of a material for the reflective electrode, an increase in the area of the reflective electrode can be taken into account in order to improve luminous efficacy of the light emitting diode. For example, when an electrode formed on the p-type semiconductor layer is used as the reflective electrode, an upper surface of the p-type semiconductor layer, that is, an upper surface of a mesa structure, is increased as much as possible in view of improvement in luminous efficacy.
However, a decrease in distance between the reflective electrode and the periphery of an upper surface of the mesa structure causes an increase in the possibility of current leakage and has a limitation in improvement of luminous efficacy.
In order to improve light output in the flip chip structure, a technique of reducing light loss by disposing a distributed Bragg reflector on a side on which electrodes are formed can be considered. The distributed Bragg reflector (DBR) is formed by alternating layers having different indices of refraction and generally provides high reflectance over a broad range of wavelengths. In general, a DBR composed of 20 pairs of layers is used to provide high reflectance over a wide wavelength range of 400 nm to 700 nm. However, such a DBR has a large thickness of about 4 μm, making it difficult to perform patterning, and a large side inclination of the DBR makes it difficult to form an electrode on the DBR.
On the other hand, light emitting diodes are modularized into a light emitting device module when used in a final product. In general, the light emitting diodes have been fabricated into a package through a packaging process and then mounted on a printed circuit board. Recently, however, a technique for fabricating a light emitting device module using the light emitting diodes directly mounted on the printed circuit board without the packaging process is used in the art.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and, therefore, it may contain information that does not constitute prior art.